I'll have to come clean and admit to following NCIS. Why the unease at this admission? Perhaps because it is unashamedly comfort television rather than challenging drama. But I recon there's room for a little comfort food in every balanced diet.
So - without giving anything away that hadn't been well trailed before the broadcast - one of the central core of characters dies at the end of the penultimate episode and the investigation then follows through to its conclusion. NCIS has done this before, cutting out and replacing core characters.
I'd like to compare the NCIS formula to three other screenwriting recipes:
First, the obvious comparison. CSI. Both seem to be about the investigation of crimes using forensics. NCIS is a federal naval investigation setup. CSI is linked to the regular police investigating homicide. I'm no expert on these things, but it seems vanishingly unlikely that either reflects reality. Each has a small team of investigators doing everything from shaking test tubes to arresting suspects. On the surface that makes them more or less identical.
The key difference is that CSI is primarily about the crimes and their investigation, whereas NCIS is primarily about the characters and their relationships. (Each has elements of both, but the ballance is different). Take the NCIS season 5 finale as an example. Looking back on it, the crime detection aspect was more or less irrelevant and the big hook at the very end was concerned with a threat to the relationships between the characters.
Perhaps NCIS is more similar to long running relationship-based TV dramas such as Alley McBeal. In each we have a small group of individuals with characteristics simple enough to be defined in a couple of sentences. With each, the events are secondary to the relationships.
However, Alley McBeal retained the same central cast from start to finish, whereas NCIS is prepared to kill off a central character and reshuffle the deck from time to time. Without reshuffle, a relationship drama is more or less doomed to eventual plot burnout. Other examples of this are Northern Exposure and Sex and the City. By the final season a good proportion of viewers are shouting at the television: "Get married and have done with it!"
All the above examples are American. It seems to me that the team writing and studio system practiced in America tends to produce excellent quality of material but will only stop for commercial reasons. The British system - which seems to give more control to a single writer, or possibly a very small team - doesn't always sustain the same high-quality for long, but it knows when to pull the plug for artistic reasons.
What about a movie plot? I'll use the crime movie Insomnia as an example. It too is about the detection of a crime using forensics. It too is driven by questions of character. But where the plot of an NCIS episode usually brings the characters back to more-or-less the place they started, the plot of Insomnia takes the central character to a completely different place. The journey is completed. There is no room for another episode.
My question is - have the writers of NCIS got a system for avoiding plot burnout? I guess I'll have to wait for season 6 to find out.
(Please, if you live in the US and have already got to season 6 - no spoilers in comments!)